Preparation and characterisation of Au/InGaP/GaAs Schottky barriers for radiation damage investigation E. Gombia a, , R. Mosca a , D. Pal a , S. Busi b , L. Tarricone b , P.G. Fuochi c , M. Lavalle c a Istituto IMEM-CNR, Parco Area delle Scienze 37/A, Fontanini, Parma 43010, Italy b Dipartimento di Fisica, Istituto Nazionale di Fisica della Materia, Parco Area delle Scienze 7a, Parma 43100, Italy c Istituto FRAE-CNR, Area della Ricerca, via P. Gobetti 101, Bologna 40129, Italy Received 16 May 2002; accepted 23 September 2002 Abstract High quality Au/InGaP Schottky diodes have been prepared as efficient test structures for a study of the radiation hardness of InGaP as space solar cell material. A detailed characterisation of the metal  /semiconductor barriers obtained on both n (free carrier concentration ranging from 3 /l0 15 to 1.2 /l0 18 cm 3 ) and p-type (3.5 /10 17 cm 3 ) InGaP epitaxial layers lattice matched to GaAs substrate has been performed using current  /voltage, capacitance /voltage and internal photoemission techniques. Excellent electrical properties were found for low doped (ideality factor of 1.05  /1.06, rectification ratio of about 10 10 at 0.7 V, reverse current lower than 1 /10 12 A at  /2 V) as well as heavily doped samples (rectification ratios of about 10 5 at 0.6 V). The barrier height values calculated by the different techniques were compared and discussed. Deep level transient spectroscopy (DLTS) spectra obtained on unirradiated samples did not show detectable deep levels with the exception of the heaviest doped sample showing a weak peak associated to the DX centre. After electron irradiation at 9 MeV with doses ranging from 5 /l0 13 to 1.5 /10 15 e cm 2 the samples exhibited a broad dominant peak (activation energy in the 0.90  /0.93 eV range) whose intensity increased linearly with the absorbed dose. The broadening of the peak and the observed increase of the corresponding trap concentration with the doping level suggest that this peak could be associated to complexes due to the interaction of primary defects, created by high irradiation energy, with each others and with the shallow impurities. # 2002 Elsevier Science B.V. All rights reserved. Keywords: InGaP; Schottky barriers; Barrier height; Deep level transient spectroscopy 1. Introduction A growing interest exists for the application of the wide gap ternary alloy InGaP in short wavelength optoelectronic devices [1,2]; in particular, InGaP lattice matched to GaAs appears as a real alternative to the AlGaAs/GaAs system for the realisation of Al-free high quality and high reliability devices [3]. In fact the InGaP/GaAs system has some superior features with respect to the AlGaAs/GaAs one, such as: (i) lower oxidation and surface recombination rate; (ii) low propagation velocity of dislocations; (iii) a minor effect of deep level centres (DX-like); (iv) availability of selective etching techniques; (v) an attractive opportu- nity of designing the band gap line-up, so that high performance opto-electronic devices (light emitting diodes, lasers [4]), photonic devices [5] and electronic devices (amplifiers, HBT, TEGFET [6  /9]), have been reported. Moreover, it has been shown that under proper growth conditions, the band structure of the InGaP ternary alloy is strongly modified, owing to the formation of domains exhibiting a long range order [10], with substantial effects on the optical and electrical properties of the material [11,12]. Beyond its funda- mental relevance, the ordering effect might assume an increasing technological importance, depending on the opportunity of the engineering properties of the material for the development of new photonic devices [13].  Corresponding author. Fax:  /39-0521-26-9206 E-mail address: gombia@maspec.bo.cnr.it (E. Gombia). Materials Science and Engineering B97 (2003) 39  /45 www.elsevier.com/locate/mseb 0921-5107/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0921-5107(02)00393-8